Panasonic

All posts tagged Panasonic

I am a new GH4 owner and in fact it is my first DSLR-type camera. In doing some test shoots, and getting to know my camera an how it works, I ran into some troubling issues with noise in low light. Now I know that the GH4 isn’t the best in low light, compared to a Canon 5D or Sony A7s, but I had seen some good low light footage so I know it should be possible given a fast lens and some care.
Here is a good example of a low light video:

Also, I neglected to check the audio levels at the time, so the audio is over-modulated. But let’s get back to the video….

What bothered me most about the image was the blue/purple color noise pretty much all over the image.
Now I was shooting with a slow lens, the Lumix 14-45 (2.8-3.5) at 1600 ISO. But the image should be better than that, right? And indeed it should.
I dug a little deeper and discovered the secret to the GH4 is in the Profile settings and black levels.

The ISO Noise Test:
In my test, I decided to record with the lens cap on, to get a pure black image and then adjust the ISO with various profile settings to see what happens.
After recording black at C4K and incrementing the ISO, I did a split screen in a 1920×1080 sequence in Autodesk Smoke and placed a resize 4K to 1080 on one side and a center cut image on the other. This means that the noise on the resized clip should be smaller and in the other you will see a 1 to 1 pixel cut of a 4K image in a 1080 sequence.

After that I added some text to explain each setting, and then added a Color Correct effect to boost the black levels and contrast a bit to make the noise that is present more visible.
I boosted the black levels and only the black levels via an offset control 200% and increased contrast 200%. I am a 25 year professional broadcast video editor and look at images for a living. So I confident that manipulation of the black values to look into the blacks of the image is perfectly acceptable and not altering the image at all. It is just allowing me to see what’s really there. Autodesk Smoke also processes it’s images in 16bit fp.

What these tests show is the native noise being produced by the camera at high ISO settings. Certain camera settings seem to produce this purple noise in the image that I was seeing in my low light test. This image is an 800% enlargement of the 4K original.

You can see the various tests in this playlist. iDynamic & iResolution were both off for all examples.

But let me highlight a few…

In searching the internet for best practices I ran across a post by RaiChu here…

His settings were a disaster with this test. What I found overall was that boosting the Master Pedestal increased noise across all ISO settings. In RaiChu’s settings above, I found noise even at 200 ISO. [This image is an 800% enlargement of the 4K original.]
More at 1600 ISO
And tons more at 6400 ISO

In contrast using Cine D [-5,-5,-5,-5,0] Shadows/Highlights 0/0, and Master Pedestal 0, I found much less of an issue with noise.

200 ISO [This image is an 800% enlargement of the 4K original.]
and at 6400 ISO
You can still seem a few purple blocks of noise, but nothing compared to the amount introduced with the Master Pedestal set to +15.

Filmmaker James Miller, released a video showing his settings that seem to have people excited. And it too uses an increase in the master pedestal.

This video was shot at 800 and James says that that’s about the limit for the camera. Well, I would guess that it’s the limit for this profile choice as raising the master pedestal is disastrous over 800 ISO.

Other people are fond of creating am inverted S curve with the Shadows/Highlights. In fact, the popular grading software FilmConvert stated that for their purpose, users should create an inverted S curve with +5 Shadows and -5 Highlights to preserve dynamic range with the Cine D Profile.

But in my test, I find that increasing the Shadows at all in Shadows/Highlights will create more noise as you increase ISO.

Now granted, it’s not as much as raising the master pedestal, but it is there. Check out the 800% blow up images.
3200 ISO

6400 ISO

Again, not as much as master pedestal, but far more than Cine D [-5,-5,-5,-5,0] and Shadows/Highlights 0/0.

Conclusion:
In my opinion I would recommend never adjusting the master pedestal unless you are trying to match levels with another camera. Even Panasonic doesn’t endorse it’s use in trying to achieve a LOG look to your video. I would also shy away from pushing the Shadows/Highlights too far. even at +2 there was some added noise, but definitely useable. It appears that the profiles used as default [0,0,0,0,0] or even [-5,-5,-5,-5,0] doesn’t seem to increase the noise floor at all, so those adjustments shouldn’t hurt the image quality.

By no means is this test conclusive as I am simply recording black and looking for native noise produced by the camera. Obviously shooting real images, with tones and textures will affect how the camera processes the image under the various profiles.

In my original example of the musician, I also had my Shadows/Highlights at +5/-5 which added to the noise. So know I know better.

For a while after reading some posts and hearing of a possible “bad sensor” I was concerned that I perhaps got a lemon. But I think I have convinced myself that it’s all about how the camera is set up.